The present invention relates generally to fluid flow, and more particularly to a flow matching method and system using two transducers.
Certain procedures require the matching of two fluid flows. Conventional flow matching systems use a finely calibrated flow rate transducer to measure the flow rate in the first flow path and use another finely calibrated flow rate transducer to measure the flow rate in the second flow path. A valve in the first flow path is controlled such that the reading of the finely calibrated flow rate transducer in the first flow path matches the reading of the finely calibrated flow rate transducer in the second flow path.
What is needed is an improved method for matching first and second flows and an improved fluid flow matching system useful, for example, in performing kidney dialysis.
A first method of the invention is for matching the flow rate of first and second fluid flows in respective, fluidly-unconnected first and second flow paths, wherein the first flow path includes a first flow source and a first flow-rate transducer, and wherein the second flow path includes a second flow source and a second flow-rate transducer. The first method includes steps a) through g). Step a) includes shutting off the second flow source. Step b) includes fluidly interconnecting the first and second flow paths creating an interconnected flow path which allows substantially the same flow from the first flow source to encounter the first and second flow-rate transducers. Step c) includes, after steps a) and b), obtaining readings from the first and second flow-rate transducers for various identical values of the flow rate of the first flow source. Step d) includes, after step c), disconnecting the fluid interconnection between the first and second flow paths. Step e) includes turning on the second flow source. Step f) includes, after steps d) and e), obtaining a reading from the first flow-rate transducer and a reading from the second flow-rate transducer. Step g) includes controlling the flow rate of the first fluid flow to match the flow rate of the second fluid flow using the readings from step f) and using the readings in step c).
A second method of the invention is for matching a property of first and second fluid flows in respective, fluidly-unconnected first and second flow paths, wherein the first flow path includes a first flow source and a first flow transducer which measures the property, and wherein the second flow path includes a second flow source and a second flow transducer which measures the property. The second method includes steps a) through g). Step a) includes shutting off the second flow source. Step b) includes fluidly interconnecting the first and second flow paths creating an interconnected flow path which allows substantially the same flow from the first flow source to encounter the first and second flow transducers. Step c) includes, after steps a) and b), obtaining readings from the first and flow transducers for various identical values of the property of the first flow source. Step d) includes, after step c), disconnecting the fluid interconnection between the first and second flow paths. Step e) includes turning on the second flow source. Step f) includes, after steps d) and e), obtaining a reading from the first flow transducer and a reading from the second flow transducer. Step g) includes controlling the fluid flow in one of the first and second flow paths to match the property of the first and second fluid flows using the readings from step f) and using the readings in step c).
In a first expression of an embodiment of the invention, a fluid flow matching system includes a first fluid flow path, a second fluid flow path, a fluid interconnection path, and data. The first fluid flow path has a servo-controlled actuator which controls a property of the first fluid flow and has in series a first flow source, a first flow transducer, and a first valve. The second fluid flow path has in series a second valve and a second flow transducer. The fluid interconnection path has in series a first end, an interconnection valve, and a second end. The first end is in fluid communication with the first fluid flow path between the first valve and the first flow transducer. The second end is in fluid communication with the second fluid flow path between the second valve and the second flow transducer. The data represent readings of the first and second flow transducers for various identical values of the property of the first flow source taken with the first valve fully shut, the interconnection valve fully open, and the second valve fully shut. The servo-controlled actuator is controlled from readings of the first and second flow transducers taken with the first valve fully open, the interconnection valve fully shut, and the second valve fully open and from the data.
In a second expression of an embodiment of the invention, a fluid flow-rate matching system includes a first fluid flow path, a second fluid flow path, a fluid interconnection path, and data. The first fluid flow path has in series a first flow source, a servo-controlled valve, a first flow-rate transducer, and a first valve. The second fluid flow path has in series a second valve and a second flow-rate transducer. The fluid interconnection path has in series a first end, an interconnection valve, and a second end. The first end is in fluid communication with the first fluid flow path between the first valve and the first flow-rate transducer. The second end is in fluid communication with the second fluid flow path between the second valve and the second flow-rate transducer. The data represent readings of the first and second flow-rate transducers for various identical values of the flow rate of the first flow source taken with the first valve fully shut, the interconnection valve fully open, and the second valve fully shut. The servo-controlled valve is controlled from readings of the first and second flow-rate transducers taken with the first valve fully open, the interconnection valve fully shut, and the second valve fully open and from the data.
Several benefits and advantages are derived from one or more of the methods and/or expressions of the embodiment of the invention. The matching of one fluid flow to another fluid flow, such as matching the flow rate of the replacement water stream to the flow rate of the waste water stream in kidney dialysis, is accomplished without having to use calibrated flow transducers. Using uncalibrated flow transducers reduces costs.